Tv personality Nick Cannon has attempted to reach out to his former All That co-star Amanda Bynes amid concerns about her mental wellbeing, but he could not get in touch with her management team.

Mariah Carey's husband starred alongside Bynes in the hit U.S. sketch show for three years, and he admits it's been tough for him to watch the Hairspray star's life play out in the headlines thanks to her months of bizarre behaviour and recent drug possession arrest.

He tells American radio host Howard Stern, "That's like my little sister. To see someone you've seen at nine and you know she was running around with a snotty nose, and now to see her like that, it's like, wow, man. It's sad."

But Cannon reveals he has been unable to make contact with the 27 year old to offer his support - because she's ditched her manager and publicist.

He adds, "I tried to reach out... She doesn't have any of her people (staff members) anymore."

Cannon isn't the only former pal reaching out to Bynes - Lance Bass and celebrity blogger Perez Hilton have also shared their concerns for the embattled actress, while her former The Amanda Show co-star Drake Bell and Hairspray castmate Nikki Blonsky have both revealed they are in contact with her - and she's fine.

Bell recently told America's Ok! magazine, "I talk to her every day. She's a sweetheart... She's good, and she's healthy... She's in a place right now where she is searching. She's ready to be her own person, and do her own thing... She is a girl who is finding herself... Anytime I've ever been with Amanda, she's totally coherent, totally there, totally everything."